BQ76PL455A: bq76PL455A / Daisy-chain via connector and cable

S.Satoshi

Part Number: BQ76PL455A

Hi,

Now my customer is considering bq76PL455A and then they have some concern as below. Can you see it and give your opinion?

[Situation]

Customer would like to daisy-chain PL455As but they are not located in the same chassis so COMMH/L lines should be connected via connector and cable. Then they have concern if this may not be recommended because the communication error will be happened due to EMI noise to cable in noisy environment.

[Question]

Then, can you recommend such use case and share the example of cable or connector for COMMH/L lines?

Best Regards,

Satoshi / Japan Disty

over 7 years ago

0 David Wiest Jr over 7 years ago

TI__Genius 11480 points

Hello Sonoki,

I believe this is a common use case, but yes EMI is a potential concern. How long of a cable do they plan on using?

Section 5.2.2 of the EVM user guide talks about the connecters used on the EVM. The user guide is found here: http://www.ti.com/lit/ug/sluuba7a/sluuba7a.pdf

Some things to consider:

Use twisted pair cable. The shorter the cable the better.
Use proper filtering. This will largely depend on the system design and cable length

Additionally, please refer to section 8.1.2.2 of the datasheet (found here: http://www.ti.com/lit/ds/symlink/bq76pl455a-q1.pdf). This describes the isolated communication setup.

The bq76PL455A-Q1 Design Considerations app note should also be considered: http://www.ti.com/lit/an/slua791/slua791.pdf

0 S.Satoshi over 7 years ago in reply to David Wiest Jr

Guru 21675 points

Hi David,

Thank you for your comment. Regarding the length of cable, now they are planning to evaluate 300mm and 500mm cable. Do you think such length is reasonable for daisy chain?

Best Regards,
Satoshi

0 David Wiest Jr over 7 years ago in reply to S.Satoshi

TI__Genius 11480 points

Hello Sanoki,

500mm is ~20 inches, and 300mm is ~12 inches. I think with twisted pairs of this length should be okay.

EDIT:

Sonoki, please also be aware that the specific cable also matters, because of the capacitance,etc. In particular, I strongly recommend reading section 8.1.2.2.3 of the datasheet.

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BQ76PL455A: bq76PL455A / Daisy-chain via connector and cable